Page images

means settle at Cromarty. Is he wishful of knowing much about the last elevated of our granite hill-ranges,-a range newer apparently than many of our south-country traps l_let him not hesitate to take lodgings at Cromarty. Is he curious regarding our boulder-clay ?—let him set himself carefully to examine the splendid sections which it presents in the neighbourhood of Cromarty. Does he feel aught of interest in our raised beaches kthen let him come and live upon one at Cromarty. Is he desirous of furnishing himself with a key to the geology of the north of Scotland generally? -in no place will he be able to possess himself of so complete a key as among the upturned strata of Cromarty. Had he to grope his way along a course of discovery, he might find the district yielding up its more interesting phenomena but slowly : to know its Lias deposits thoroughly would be a work of months, and to know its Old Red Sandstone, a work of years; but with some intelligent guide to point out to him the localities to which his attention should be directed, and all in them that has been done and observed already, he would find that much might be accomplished in the course of a single week,-especially in the long calm days of July, when the more exposed shores of the district, with all their insulated stacks and ledges, and all their deepsea caves, may be explored by boat.



We swept downwards through the noble opening of the Cromarty Firth, and landed under the southern Sutor, on a piece of a rocky beach, overhung by a gloomy semicircular range of precipices. The terminal points of the range stand so far out into the sea, as to render inaccessible, save by boat, or at the fall of ebb in stream tides, the piece of crescent-shaped beach within. Each of the two promontories is occupied by a cave in which the sea at flood stands some ten or twelve feet over the gravel bottom, and there are three other caves in the semicircle, into which the tide has not entered since it fell back from the old coast line. The larger and deeper of the three caves in the semicircular inflection is mainly that which we had landed to explore. It runs a hundred and fifty feet into the granitic rock, in the line of a fault that seems first to have opened some eight or ten feet, and then, leaning back, to have closed its sides atop, forming in this way a long angular hollow. It has borne for centuries the name of the Doocot (i.e., Dove-cot) Cave, and has been from time immemorial a haunt of pigeons. We approach the opening : there is a rank vegetation springing up in front, where the precipice beetles over, and a small stream comes pattering in detached drops like those of a thunder-shower; and we see luxuriating under it, in vast abundance, the hot, bitter, fileshy-leaved scurvy-grass, of which Cook made such large use, in his voyages, as an anti-scorbutic. The floor is damp and mouldy; the green ropy sides, which rise some five-and-twenty feet ere they close, are thickly furrowed by ridges of stalactites, that become purer and whiter as we retire from the light and the vegetative influences, and present in the deeper recesses of the cave the hue of statuary marble. The last vegetable that appears is a minute delicate moss, about half an inch in length, which slants outwards to the light on the prominences of the sides, and overlies myriads of similar sprigs of moss, long since converted into stone, but which, faithful in death to the ruling law of their lives, still point, like the others, to the free air and sunshine. As we step onwards, we exchange the brightness of noon for the mellower light of evening. A few steps further, and evening has deepened into twilight. We still advance; and twilight gives place to a gloom dusky as that of midnight. We grope on, till the rock closes before us; and, turning round, see the blue waves of the firth through the long, dark vista, as if we viewed them through the tube of some immense telescope. We strike a light. The roof and sides are crusted with white stalactites, that depend from the one like icicles from the eaves of a roof in a severe frost, and stand out from the other in pure, semi-transparent ridges, that resemble the folds of a piece of white drapery dropped from the roof; while the floor below has its rough pavement of stalagmite, that stands up, wherever the drops descend, in rounded prominences, like the bases of columns. The marvel has become somewhat old-fashioned since the days when Buchanan described the dropping cave of Slains,—'where the water, as it descends drop by drop, is converted into pyramids of stone,'-as one of the wonders of Scotland, and deemed it necessary to strengthen the credibility of his statement by adding, that he had been informed by persons of undoubted veracity that there existed a similar cave among the Pyrenees.' Here, however, is a puzzle to exercise our ingenuity. Some of the minuter stalactites of the roof, after descending perpendicularly, or at least nearly so, for a few inches, turn up again, and form a hook, to which one may suspend one's watch by the ring; while there are others that form a loop, attached to the roof at both ends. Pray, how could the descending drop have returned upwards to form the hook, or what attractive power could have drawn two drops together, to compose the elliptical curve of the loop? The problem is not quite a simple one. It is sufficiently hard at least, as it has to deal with only half-ounces of rock, to inculcate caution on the theorists who profess to deal with whole continents of similar material. Let us examine somewhat narrowly. Dark as the recess is, and though vegetation fails full fifty feet nearer the entrance than where we now stand, the place is not without its inhabitants. We see among the dewy damps of the roof the glistening threads of some minute spider, stretching in lines or depending in loops. And just look here. Along this loop there runs a single drop. Observe how it descends, with but a slight inclination, for about two inches or so, and then turns round for about three quarters of an inch more; observe further, that along this other loop there trickle two drops, one on each side ; that, as a consequence of the balance which they form the one against the other, their descent has a much greater sweep; and that, uniting in the centre, they fall together. We have found a solution of our riddle, and received one proof more of the superiority of the simple art of seeing over the ingenious art of theorizing.

But let us proceed to the proper business of the excursion. We have provided ourselves with tools for digging ; and, selecting a spot some thirty feet within the cavern, where the tom seems composed of a damp dark mould, we set ourselves, with spade and pick-axe, to penetrate to the sea-gravel beneath. The soil yields as easily to the tool as a piece of garden-mould; and turning it up to the light in cubical adhesive masses, we find it consisting of an impalpable brown earth, that exactly resembles raw umber. We have fallen on a bed of pure guano, not quite so rich, perhaps, as that which our agriculturists export from the rocky islets of South America at the rate of about fourteen pounds per ton, for it must have been formed originally of vegetable, not animal matter, and we find that it lacks the strong ammoniacal smell of the guano produced by predacious water-birds; but judging from its appearance, and from the high estimate formed of old of the dung of pigeons as a manure, it must be of value enough to deserve removal from the damp unproductive floor of the Doocot. We find the bed which it composes extending downwards from two to three feet, and filling the cavern from side to side. A rock-gravel lies below, hardened into an imperfect breccia by a ferruginous cement; but the rotting moisture exuded from the guano has been unfavourable, apparently, to the preservation of shells, and we find that it contains nothing organic. We again remove to the inner recesses of the cave. Mark, first, that peculiar appearance along the sides. There stands out, at the height of about four feet from the present floor, what seems a rude projecting cornice of rockgravel, bound together by the stalactitical cement: the projection at one point somewhat exceeds eighteen inches; and we find it bearing short-stemmed stalagmites atop, just like the rugged pavement below. To use a homely but apt illustration, the appearance is that presented by the lower part of a tallow-candle that had been burning exposed to a current of air, with its grease running down in ridges on the sides, and then spreading out on the margin of the metasocket, when, after raising it out of the candlestick, we see the lower accumulation projecting from it like a cornice. That line of projecting gravel indicates the level at which the floor of the cavern once stood. If we remove the looser parts of the present floor, we shall find its place indicated by just a similar line of projection. The loose sea-gravel could have adhered to the sides only by having formed the part of the floor in contact with them, until the stalagmitical substance had taken effect upon it, by binding it into a mass, and fixing it where it had lain. Let us break into one of the projections. We find it a true breccia, thickly interspersed with such fragments of shells as we may pick up by hundreds in the neighbouring sea-caves, where the incessant beat of the surf on the hard rocks against which it dashes breaks them into rounded fragments. There, for instance, is a massy little bit of the strong smooth buckie (Fusus Antiquus), the largest of British univalves; and there a fragment equally massy of the Icelandic Venus, -both of them productions of the oceans, and of such rivers as the Firths of Cromarty and Dornoch. The materials of the projecting cornice are those of a cavern-beach much exposed to the roll of the surf.

[ocr errors]
« ՆախորդըՇարունակել »